The Metropolitan Police is to be investigated over whether it could have prevented trouble at a funeral that resulted in the death of an innocent bystander.
Azezur Khan, 21, was gunned down in East Dulwich, south-east London, last Thursday after attending the service for road crash victim Joel James Lee Morgan, 17, at a nearby cemetery.
Joel's mother requested a police presence at the funeral because she feared trouble, it has emerged.
It is understood that officers attended the earlier church service and the wake, but not the funeral service where the shootings broke out.
The Met made a voluntary referral to the Independent Police Complaints Commission (IPCC) "in relation to information received by them prior to the fatal shooting", the IPCC said.
In a statement, IPCC Commissioner Sarah Green said: "Following the tragic death of Azezur (Ronnie) Khan, who was shot and killed while attending a funeral in Forest Hill Road, South London, on November 3 2011, the Metropolitan Police referred the matter to the IPCC. We have decided to conduct an independent investigation into the information held and actions taken by the police prior to the incident."
Several shots were fired shortly after mourners left the cemetery on November 3. Mr Khan, known as Ronnie, was shot near the junction of Forest Hill Road and Rockells Place at around 3pm. He was declared dead at the scene, and a post-mortem examination gave the cause of death as a single gunshot wound to the abdomen.
A 17-year-old boy was taken to hospital after he was shot in the ankle.
Two 17-year-old girls and two 20-year-old men were arrested over the incident and were bailed to late November.
Last week police said the boy whose funeral it was had "contact with gang members".